The Coverline system joins polyethylene tubes with aluminium couplings to obtain uniform water application. These systems generally consist of a network of main pipes, a group of hydrants and the laterals. The sprinklers are assembled on aluminium risers of different heights (up to 3m). The Coverline system uses lever lock union and half turn couplings. They are easy to handle due to their lightness, environmental resistance and resistance to chemical and mechanical damage. This system alleviates the problems with frequently having to move pipework.

The patented system COVERLINE® for sprinkling irrigation developed by the company SALEPLAS S.L. joins polyethylene tubes with aluminium couplings in order to obtyain a solid set sprinkler irrigation system which guarantees the uniformity of water application. With this durable system a longer lasting installation is achieved. The characteristics of polyethylene tubes, resistant to chemical agents and more resistant to damage, COVERLINE® is adapted to extend existing aluminium solid sets; as well as drip inrrigation installations.

The aim of all sprinkler irrigation systems is to achieve the best uniformity and efficiency possible in the application of water. This objective derives from the growing demand of the scarcity of available water resources. That’s why, and in answer to the requirements of farmers, SALEPLAS, S.L. manufactures the patented system, COVERLINE.

COVERLINE is a modular system, which combines aluminium couplings with the high density polyethylene tubes. This system is classified, as a temporary fixed stationary system (air solid set). This type of solid set consists of a network of main pipes and laterals for irrigation. These laterals can be installed permanently or only for the season, being transferred to other zones or to another plot according to the rotation of crops in the agricultural business.

With any irrigation system it is necessary to remember that the main resources managed are: water, energy, manpower and equipment. We should achieve the combination of these factors in every particular situation that leads to the economic optimum, and in accordance with the conditions of the growing medium (soil, climate, crop, plot distribution, etc).

A solid set sprinkler irrigation system generally consists of a network of main pipes, with a group of hydrants, to which are connected the secondary pipes and the laterals. In the COVERLINE system the secondary pipes and the laterals of irrigation are manufactured in high density polyethylene with aluminium couplings. The nominal pressure of these tubes used for solid set is 6 atm.

The COVERLINE system has high density polyethylene tubes with outside diameters 50, 63, 75, 90 and 110mm, available in hook, lever and half turn couplings. Everything is complemented with a large range of accessories (elbows, tees, crosses, reductions and reversals) in order to supply any irrigation system design. The sprinklers are assembled on aluminium canes of different heights (up to 3m), having their own coupling to the polyethylene tube and a stabilizing plate. COVERLINE also allows you, in a quick and reliable way, to make all connections to the sprinkler and drip irrigation systems. It’s a system perfectly adapted to large plots and irregular or smaller ones.

The couplings of these polyethylene tubes can be spherical, with mechanical closing by lever lock to achieve total water tightness to any pressure; or hydraulic with bilabial joint. In the first case the hermeticism is perfect, while in the second case, the seal is obtained by the hydraulic pressure of the water that circulates inside the tube when it achieves a pressure above 0,5 atmospheres. The COVERLINE® system uses the following connection options:

Mechanical type Union (water tightness closing): Lever lock

Hydraulic type Union: Hook or half turn

The couplings are adapted to extend aluminium solid sets already installed. The tubes have the stiffness for use up to 12m lengths. SALEPLAS, S.L. is able to manufacture them up to 12m lengths. They are easy to handle due to their quick couplings and lightness, having resistance to environmental cracking, chemical products and mechanical damage. The COVERLINE® system also has other advantages:Reliability, with total water tightness to low pressures.

This system solves the handling, coiling and storage of the thick pipes used in drip irrigation (main and secondary).

The most common irrigation frames in the COVERLINE® system are: 12m x 12m and 14m x 16m in diamond or in triangle. The configuration will depend on the characteristics of the soil, dominant wind directions, rainfall, and type of sprinklers installed.

This system is quite extensive in areas of Spain like Castilla y Leon, Andalusia and Castilla La Mancha, where the sugar beet cultivation forces the rotation of irrigated plots. In all of these areas it is also used for the irrigation of cereals. In Extremadura it’s used for the irrigation of tobacco plantations and in Andalusia also for the cotton. In the eastern area of Spain their use is mainly for horticulture like lettuce growing.

In case of irrigation on solid set, we can obtain energy savings of 25% when the uniformity of emission will be greater than 85% and the working pressure is around 3-4 bar. In the U.K. the COVERLINE® system is extremely versatile and can be used for salad crops, potatoes, carrots and herbs depending on frame size and nozzle size.

Characteristics of sprinkler irrigation with solid set are derived mainly from two fundamental aspects:

The control of the irrigation is only limited by the atmospheric conditions (evaporation or drag losses and the effect of the wind on the uniformity of distribution).

The uniformity of application is independent of the hydro physical characteristics of the soil.

Keeping in mind the afore-mentioned aspects we can enumerate a series of characteristics that confer several advantages to this system over other irrigation methods.

The sprinkler irrigation with solid set can be used in a great variety of soils, even on those that demand frequent and slight watering, since the quantity of water applied is only a question of the length of times.

This system is adapted to the rotation of crops and to recovery irrigation.

The nozzles of the sprinklers will be less obstructed with correct filtration.

When the water applied with sprinkler irrigation infiltrates in the soil, it adds oxygen activating the humus generation process.

The system adapts itself to undulating topographies. This helps to preserve the natural fertility of the soil, and avoids soil and mineral leaching.

A high rate of automation can be achieved, with less manpower costs.

Low rates of application can be achieved for seed germination, water saving and to avoid capping and consolidation of soil structure.

Summary of management suggestionsWith the purpose of establishing a series of general guidelines to keep in mind when designing and managing sprinkler irrigation systems, such as the COVERLINE® system, the following summary of recommendations can be used for the correct management of the sprinkler irrigation:

A higher coefficient of uniformity (CU) is achieved using two nozzles on the sprinkler rather than only one; with “extended case” or larger nozzles for wind speeds higher than about 2 m/s.

Pressures of more than 400 kPa should be avoided, because they produce a greater proportion of small water drops (apart from the higher economic cost).

Design the systems with lower applications (6-8 mm/h) so that, besides avoiding the problems of forming puddles and run-off, the time of irrigation would be less. By this way higher values of CU are obtained, and the distortions produced by the wind are partly compensated.

Don’t irrigate with strong winds, since the uniformity of distribution of the water applied decreases considerably. Also, with high wind speeds, the percentage of evaporation or drag losses increases.

Application of night watering. Irrigating at night reduces the value of the evaporation and drag losses since the wind speed and the temperature of the air is lower than during the day; the energy cost per kWh is also lower. To carry out night watering, the most appropriate thing is to automate the irrigation system.

Carry out appropriate maintenance of all elements of the installation. In many cases the lack of uniformity of the sprinkler irrigation systems is due to: plugged or broken emitters, low pressures for lack of cleaning in the filters, etc.

Other applications of the COVERLINE® systemThe sprinkler irrigation with the COVERLINE® system can be used under certain conditions for:

Microsprinkler irrigation, when sprinklers or sprayers of low pressure and small radius are used.

Sprinkler irrigation for frost defence.

Mineral plant nutrition by means of the sprinkler equipments.

Organic plant nutrition using the sprinkler equipments

Flowering delay.

Distribution of residual waters.

It is important to note that except for the mineral plant nutrition, the use of the irrigation system for the distribution of chemical products need very exact concentrations and uniform distribution. This may be complicated if the system is not very well designed and managed, with important risks of contamination or damage.

It’s also necessary to remember that the capacity of the frost defence sprinkler system must cover the whole area to protect simultaneously. To reduce the installation costs it’s usual to divide the irrigation area in to sectors. When the system will be used to irrigate and for frost defence, it would be necessary to endow the installation with a complimentary supply of pressured water that allows combined operation of the area.

ConclusionsUsing the COVERLINE® system for solid set, made up of high density polyethylene tubes with aluminium couplings, a longer life for this type of installation is achieved due to the characteristics of the polyethylene, a material resistant to chemical agents, durable in the open, and resistant to chemical damage. The low specific weight and the flexibility of the polyethylene tubes also facilitate ease of transport, assembly and handling of the irrigation installation.

We must remember too that the efficient use of water by farmers requires continuous information about the water consumption of the crops. It is fundamental also to know and to control the main factors that take part in the process of irrigation: the pressure and the rain as controllable factors; and the wind as an uncontrollable factor. The pressure and flow are the main factors to control in a sprinkler irrigation installation. The effect of the wind is important, and its distortion effect on the uniformity of the water distribution should be reduced where possible.

Finally, everyone knows that water is a more and more scarce resource and not only in quantity, but also in quality. All of us must manage water resources with the highest efficiency as possible within the particular economic conditions that production allows.

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